As illustrated by FIG. 1, a water cooled chiller type refrigeration system 10 using a screw compressor 20 typically includes a condenser 30, a cooler 40, an oil separator 50, a condenser fan 60 and one or more expansion devices 70. The compressor 20 requires oil for lubrication, wherein the oil is typically entrained in a refrigerant. The combined oil and refrigerant mixture is carried through a compression cycle and discharged into the oil separator 50, where the oil must be removed from the refrigerant to allow for proper operation of the cooler 40. From the oil separator 50, the clean refrigerant flows to the condenser 30 and the separated oil is returned to the compressor 10.
Most known oil separators, such as those described in U.S. Pat. No. 5,704,215 to Lord et al. (the entirety of which is incorporated by reference herein), perform this separation function well. However, it has been observed that high noise levels are often generated in the vicinity of an oil separator 50 within a refrigeration system, such as the system 100 illustrated in FIG. 1. Without wishing to be bound by theory, it is believed that this is caused by high level pressure waves/pulsations (i.e., 250 Hz or above) emanating from the compressor 20 that are transferred to the oil separator 50, which acts like a resonant cavity and thus is excited by the compressor pulsations. This excitement causes high vibration levels at the surface of the oil separator 50, and that, in turn, translates into high noise levels outputted by the oil separator. These excess noise levels can be distracting and bothersome, or, even worse, can be damaging to the hearing of those working around the oil separator 50 and/or can be in violation of applicable noise ordinances.
Previous efforts by those in the art to reduce the high noise levels produced by an oil separator 50 have focused on placing noise reduction equipment or devices between the oil separator and the compressor 20. Often, however, such equipment is subjected to high pressure differentials between the compressor discharge within the equipment and the atmosphere outside of the equipment. In such instances, the noise reduction equipment functions, in essence, as a pressure vessel, thus implicating strict design rules, certifications, and by consequence, added costs. Moreover, the added noise reduction equipment causes the refrigeration/cooling system to occupy a larger overall footprint, which is suboptimal and can even outweigh any beneficial noise reduction that actually is achieved through use of the equipment.
Therefore, a need exists for methods and apparatus to reduce the noise output of an oil separator without interfering with the functioning of the oil separator or any other equipment utilized in connection with the refrigeration system, and wherein such methods and apparatus would not be plagued by any of the various drawbacks associated with muffling apparatus known in the art.